I had a few issues with starting out
It allowed me to go past login and it offered to “add a new community.” But at the same time it is displaying a list of communities. The community I wanted to join wasn’t present so I tried “adding” but that generated an error.
I then saw that it wasn’t asking me to login to my own discourse community, but to create an account for this app. One of the beneficial behaviours of the other discourse app was that it didn’t try to own my account, I simply provided login details to the discourse web site to get in.
Having created an account I was then able to add my community to the list. On an iPhone 13 I could not see the field to enter my community name, it was hidden by the keyboard.
Once I’d got over those hurdles I was then able to login to my community and it worked quite well. I’ve always thought that discourse websites worked fairly well in mobile mode and that is improving.
After playing a little I noticed an email from Supabase asking me to confirm a signup. As I had no knowledge of Supabase I marked that email as spam and deleted it.